Read JBL E 250P (serv.man15) Service Manual online
E250P
Testing Procedure
A. Power Amp Section
Resistance
Check
Resistance from S+ (SPK O/P) to GND should be >1M
Ω
(NO LOAD)
Resistance from V+ (C6 P+) to V- (C8 P-) gradually Fully CHARGED should read >10k
Ω
Resistance from V+ (C6 P+) to S+ (SPK O/P) should read >1M
Ω
Resistance from V- (C8 P-) to S+ (SPK O/P) should read >1M
Ω
2. Power Up LED RED
With a 5mV signal to Low level input, LED should change to GREEN
-Voltage measurements (DVM)
OP AMP
LED
P-U4(1)
P-U4(7)
RED
0Vrms
11.84VDC
GREEN
7.13Vrms
-12.93VDC
3. D.C. Operation
-Voltage measurements (DVM) on CLASS D POWER AMP
Between
V+
Q4(E)
Q1(C)
Q10(C)
U7(1)
U7(2)
U7(4)
U7(6)
U7(7)
U7(8)
And This
Point
GND
V-
GND
GND
GND
GND
GND
GND
GND
GND
Get this
Reading
71.7V
0V
-71.7V
0V
-71.7V
-71.5V
-71.2V
0V
0V
4.65V
4. Check Switching Frequency
•
Oscilloscope - USE THE PROBE TIP TO U6(7) TO GND
•
Reading 100kHz +/-10%,24Vp-p
B. Pre Amp Section
Line Level Input Sensitivity
-Set up
Turn level, X’OVER FREQ POT Fully CW and LFE switch off
Generator Set at 200mV@50Hz
Signal to Line level input
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